The invention is related to a device or an apparatus for the administration of medication, and it includes a controllable dosing unit and a control or programming unit. If so desired, the programming unit may be located or positioned separately from the dosing unit.
Apparatuses or devices of this type are designed for the continuous infusion of liquid medications, such as heparin, cytostatics, analgesics, insulin and other hormones. The infusion rate can be programmed in advance; it may be constant or may vary in a cyclical manner (for example according to a daily profile) over a considerable time period. Alternatively, the infusion rate can be adjusted by hand using suitable operating elements. The infusion rate can also be adjusted to the current requirements dictated by the patient's need as detected by a sensor. When such an apparatus is used at bedside or worn on the body, a catheter is introduced from the device into the body. The apparatus can also be implanted, in which case an external control or programming unit is generally used to control and/or program the infusion rate. Apparatuses of this kind are currently available from various manufacturers, and are described in medical literature.
Continuous, controlled or programmed infusion has the advantage, in comparison with conventional forms of therapy (such as oral administration of medication or injections) that the dosage of the medication is more accurate and can be better adapted to the actual medication need or requirements, which may be constant or may fluctuate.
Under certain circumstances, however, such infusion entails a disadvantage as compared to conventional forms of therapy, because the introduction of medications into the body is not automatically limited to a specified dose. This can lead to an overdose which can be dangerous for the patient under certain circumstances, particularly when loss of consciousness, loss of sleep or even failure to pay attention prevents the patient from reducing or turning off the infusion when the infusion rate has been set too high. This will now be discussed with specific exemplary reference to diabetes therapy using insulin.
Devices for programmed or controlled dosing of medications are used for example, in diabetes therapy for continuous insulin infusion. The infusion rate can either be programmed in advance for a long time period (for example, with a cyclically repeating 24-hour program), or can be adjusted by the patient to his current needs, with the aid of suitable operating elements. For example, the infusion rate can be set to a fundamental basal rate that is either constant over time or programmed according to a daily profile; there can then be added at each meal a supplementary rate of limited duration. This supplementary rate takes into account the higher need for insulin during the digestion of carbohydrates.
If the insulin requirement has been incorrectly estimated or if it changes unexpectedly, due, for example, to illness, mental excitement or unaccustomed bodily activity, the result may be an overdose of insulin, causing under certain circumstances a hypoglycemic condition associated with illness and even loss of consciousness. Hypoglycemic conditions of this kind are particularly dangerous when they occur during sleep, because it is then impossible to take compensatory measures (e.g. reducing or turning off completely the insulin infusion or administering glucose) promptly, and it may be impossible to take them at all. In the most serious cases, irreversible brain damage or even death of the patient can result. Whereas in conventional injections the insulin dose injected into the body is limited by the volume of the syringe and used up after a certain time, in continuous infusions the application of insulin is continued even when the patient is unconscious or otherwise incapable of acting. This is a disadvantage of automatic dosing devices as a class, and can also occur in similar manner in connection with the infusion of medications other than insulin that have critical dosages.